// -----------------------------------------------------------------------
//  <copyright file="Crc32Msb.cs" company="Henric Jungheim">
//  Copyright (c) 2012, 2013.
//  <author>Henric Jungheim</author>
//  </copyright>
// -----------------------------------------------------------------------
// Copyright (c) 2012, 2013 Henric Jungheim <software@henric.org>
// 
// Permission is hereby granted, free of charge, to any person obtaining a
// copy of this software and associated documentation files (the "Software"),
// to deal in the Software without restriction, including without limitation
// the rights to use, copy, modify, merge, publish, distribute, sublicense,
// and/or sell copies of the Software, and to permit persons to whom the
// Software is furnished to do so, subject to the following conditions:
// 
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
// 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.

namespace SM.TsParser.Utility
{
    static class Crc32Msb
    {
        // MSB CRC32 Lookup for 0x04c11db7
        // x^32 + x^26 + x^23 + x^22 + x^16 + x^12 + x^11 + x^10 + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1
        static readonly uint[] Crc32Table =
        {
            0x00000000, 0x04c11db7, 0x09823b6e, 0x0d4326d9,
            0x130476dc, 0x17c56b6b, 0x1a864db2, 0x1e475005,
            0x2608edb8, 0x22c9f00f, 0x2f8ad6d6, 0x2b4bcb61,
            0x350c9b64, 0x31cd86d3, 0x3c8ea00a, 0x384fbdbd,
            0x4c11db70, 0x48d0c6c7, 0x4593e01e, 0x4152fda9,
            0x5f15adac, 0x5bd4b01b, 0x569796c2, 0x52568b75,
            0x6a1936c8, 0x6ed82b7f, 0x639b0da6, 0x675a1011,
            0x791d4014, 0x7ddc5da3, 0x709f7b7a, 0x745e66cd,
            0x9823b6e0, 0x9ce2ab57, 0x91a18d8e, 0x95609039,
            0x8b27c03c, 0x8fe6dd8b, 0x82a5fb52, 0x8664e6e5,
            0xbe2b5b58, 0xbaea46ef, 0xb7a96036, 0xb3687d81,
            0xad2f2d84, 0xa9ee3033, 0xa4ad16ea, 0xa06c0b5d,
            0xd4326d90, 0xd0f37027, 0xddb056fe, 0xd9714b49,
            0xc7361b4c, 0xc3f706fb, 0xceb42022, 0xca753d95,
            0xf23a8028, 0xf6fb9d9f, 0xfbb8bb46, 0xff79a6f1,
            0xe13ef6f4, 0xe5ffeb43, 0xe8bccd9a, 0xec7dd02d,
            0x34867077, 0x30476dc0, 0x3d044b19, 0x39c556ae,
            0x278206ab, 0x23431b1c, 0x2e003dc5, 0x2ac12072,
            0x128e9dcf, 0x164f8078, 0x1b0ca6a1, 0x1fcdbb16,
            0x018aeb13, 0x054bf6a4, 0x0808d07d, 0x0cc9cdca,
            0x7897ab07, 0x7c56b6b0, 0x71159069, 0x75d48dde,
            0x6b93dddb, 0x6f52c06c, 0x6211e6b5, 0x66d0fb02,
            0x5e9f46bf, 0x5a5e5b08, 0x571d7dd1, 0x53dc6066,
            0x4d9b3063, 0x495a2dd4, 0x44190b0d, 0x40d816ba,
            0xaca5c697, 0xa864db20, 0xa527fdf9, 0xa1e6e04e,
            0xbfa1b04b, 0xbb60adfc, 0xb6238b25, 0xb2e29692,
            0x8aad2b2f, 0x8e6c3698, 0x832f1041, 0x87ee0df6,
            0x99a95df3, 0x9d684044, 0x902b669d, 0x94ea7b2a,
            0xe0b41de7, 0xe4750050, 0xe9362689, 0xedf73b3e,
            0xf3b06b3b, 0xf771768c, 0xfa325055, 0xfef34de2,
            0xc6bcf05f, 0xc27dede8, 0xcf3ecb31, 0xcbffd686,
            0xd5b88683, 0xd1799b34, 0xdc3abded, 0xd8fba05a,
            0x690ce0ee, 0x6dcdfd59, 0x608edb80, 0x644fc637,
            0x7a089632, 0x7ec98b85, 0x738aad5c, 0x774bb0eb,
            0x4f040d56, 0x4bc510e1, 0x46863638, 0x42472b8f,
            0x5c007b8a, 0x58c1663d, 0x558240e4, 0x51435d53,
            0x251d3b9e, 0x21dc2629, 0x2c9f00f0, 0x285e1d47,
            0x36194d42, 0x32d850f5, 0x3f9b762c, 0x3b5a6b9b,
            0x0315d626, 0x07d4cb91, 0x0a97ed48, 0x0e56f0ff,
            0x1011a0fa, 0x14d0bd4d, 0x19939b94, 0x1d528623,
            0xf12f560e, 0xf5ee4bb9, 0xf8ad6d60, 0xfc6c70d7,
            0xe22b20d2, 0xe6ea3d65, 0xeba91bbc, 0xef68060b,
            0xd727bbb6, 0xd3e6a601, 0xdea580d8, 0xda649d6f,
            0xc423cd6a, 0xc0e2d0dd, 0xcda1f604, 0xc960ebb3,
            0xbd3e8d7e, 0xb9ff90c9, 0xb4bcb610, 0xb07daba7,
            0xae3afba2, 0xaafbe615, 0xa7b8c0cc, 0xa379dd7b,
            0x9b3660c6, 0x9ff77d71, 0x92b45ba8, 0x9675461f,
            0x8832161a, 0x8cf30bad, 0x81b02d74, 0x857130c3,
            0x5d8a9099, 0x594b8d2e, 0x5408abf7, 0x50c9b640,
            0x4e8ee645, 0x4a4ffbf2, 0x470cdd2b, 0x43cdc09c,
            0x7b827d21, 0x7f436096, 0x7200464f, 0x76c15bf8,
            0x68860bfd, 0x6c47164a, 0x61043093, 0x65c52d24,
            0x119b4be9, 0x155a565e, 0x18197087, 0x1cd86d30,
            0x029f3d35, 0x065e2082, 0x0b1d065b, 0x0fdc1bec,
            0x3793a651, 0x3352bbe6, 0x3e119d3f, 0x3ad08088,
            0x2497d08d, 0x2056cd3a, 0x2d15ebe3, 0x29d4f654,
            0xc5a92679, 0xc1683bce, 0xcc2b1d17, 0xc8ea00a0,
            0xd6ad50a5, 0xd26c4d12, 0xdf2f6bcb, 0xdbee767c,
            0xe3a1cbc1, 0xe760d676, 0xea23f0af, 0xeee2ed18,
            0xf0a5bd1d, 0xf464a0aa, 0xf9278673, 0xfde69bc4,
            0x89b8fd09, 0x8d79e0be, 0x803ac667, 0x84fbdbd0,
            0x9abc8bd5, 0x9e7d9662, 0x933eb0bb, 0x97ffad0c,
            0xafb010b1, 0xab710d06, 0xa6322bdf, 0xa2f33668,
            0xbcb4666d, 0xb8757bda, 0xb5365d03, 0xb1f740b4
        };

        public static bool Validate(byte[] buffer, int offset, int length)
        {
            var crc32 = Compute(buffer, offset, length);

            return 0 == ~crc32;
        }

        static uint Compute(byte[] buffer, int offset, int length)
        {
            var crc32 = ~0u;

            for (var i = offset; i < offset + length; ++i)
                crc32 = (crc32 << 8) ^ Crc32Table[((crc32 >> 24) ^ buffer[i]) & 0xff];

            return ~crc32;
        }
    }
}
